Thin film transistor array panel for a liquid crystal display

ABSTRACT

A plurality of gate lines formed on an insulating substrate, each gate line including a pad for connection to an external device; a plurality of data lines intersecting the gate lines and insulated from the gate lines, each data line including a pad for connection to an external device; and a conductor overlapping at least one of the gate lines and the data lines are included. An overlapping distance of the gate lines or the data lines and a width of the conductor decreases as the length of the gate lines or the data lines increases. Accordingly, the difference in the RC delays due to the difference of the length of the signal lines is compensated to be reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.10/915,584 filed Aug. 9, 2004 and 10/359,731 filed on Feb. 6, 2003, andnow U.S. Pat. No. 6,774,414, which claims priority to Korean ApplicationNo. 01-31803 filed on Jun. 7, 2002.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a thin film transistor array panel, andin particular, to a thin film transistor array panel including a fan outarea provided with a connection connecting a signal line to a pad andlocated between a display area and a pad area.

(b) Description of the Related Art

Generally, a thin film transistor (“TFT”) array panel for a liquidcrystal display (“LCD”) or an electro-luminescence (“EL”) display isused as a circuit board for driving respective pixels in an independentmanner. The TFT array panel includes a scanning signal wire or a gatewire transmitting scanning signals, an image signal wire or a data wiretransmitting image signals, TFTs connected to the gate and the datawire, pixel electrodes connected to the TFTs, a gate insulating layercovering the gate wire for insulation, and a passivation layer coveringthe TFTs and the data wire for insulation. The TFT includes a gateelectrode, which is a part of the gate wire, a semiconductor layerforming a channel, source and drain electrodes, which are parts of thedata wire, a gate insulating layer, and a passivation layer. The TFT isa switching element for transmitting the image signals from the datawire to the pixel electrode in response to the scanning signals from thegate wire.

A plurality of driving integrated circuits (“ICs”) are connected to theTFT array panel for applying driving signals to the gate lines and thedata lines. The driving ICs are connected to the gate lines or the datalines via pads, which are clustered on a narrow area for connection tothe driving ICs. On the contrary, the distances between the gate linesor the data lines on a display area are determined by the size of thepixels to have larger values than the distances between the pads.Accordingly, a fan-out area where the distances between the signal linesgradually increase is provided between the pad area and the displayarea. The fan-out area results in the difference in the length betweenthe signal lines, thereby causing different RC delays between the signallines. The difference in the RC delay causes a difference in imagesignals resulting in a deteriorated image quality.

SUMMARY OF THE INVENTION

In accordance with the present invention, a difference in RC delaybetween signal lines of a thin film transistor array panel is reduced. Aconductor having a varying width depending on an overlapping length ofthe conductor with signal lines is provided.

According to an embodiment of the present invention, a thin filmtransistor array panel is provided, which includes: an insulatingsubstrate; a plurality of gate lines formed on the insulating substrate,each gate line including a pad for connection to an external device; aplurality of data lines intersecting the gate lines and insulated fromthe gate lines, each data line including a pad for connection to anexternal device; and a conductor overlapping at least one of the gatelines and the data lines, wherein an overlapping distance of the gatelines or the data lines and a width of the conductor decreases as thelength of the gate lines or the data lines increases.

Preferably, each data line includes a pad portion including the pad, adisplay portion, and a fan-out portion connecting the display portionand the pad portion, and width of the fan-out portion of the data lineincreases as length of the fan-out portion of the data line increases.Preferably, each gate line comprises a pad portion including the pad, adisplay portion, and a fan-out portion connecting the display portionand the pad portion, and width of the fan-out portion of the gate lineincreases as length of the fan-out portion of the data line increases.The conductor is preferably applied with a common electrode voltage. Itis preferable that the thin film transistor array panel further includesa pixel electrode located on a pixel area defined by intersections ofthe gate lines and the data lines, wherein the conductor includessubstantially the same layer and the same material as the pixelelectrode.

The conductor may overlap the gate lines, wherein the conductor includessubstantially the same layer and the same material as the data lines.The conductor may overlap the data lines, wherein the conductor includessubstantially the same layer and the same material as the gate lines.The conductor may include a first conductive segment overlapping thegate lines and a second conductive segment overlapping the data lines,the first conductive segment includes substantially the same layer andthe same material as the data lines, and the second conductive segmentsubstantially the same layer and the same material as the gate lines.The conductor may be floated.

According to another embodiment of the present invention, a thin filmtransistor array panel is provided, which includes: an insulatingsubstrate; a plurality of gate lines formed on the insulating substrate,each gate line including a pad for connection to an external device; agate insulating layer formed on the gate lines; a plurality of datalines formed on the gate insulating layer and intersecting the gatelines, each data line including a pad for connection to an externaldevice; a passivation layer formed on the data lines; and a conductoroverlapping at least one of the gate lines and the data lines via atleast one of the gate insulating layer and the passivation layer.

It is preferable that an overlapping distance of the gate lines or thedata lines and a width of the conductor decreases as the length of thegate lines or the data lines increases. Preferably, RC delays of thegate lines are substantially the same as each other, and RC delays ofthe data lines are substantially the same as each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a layout view of a TFT array panel according to an embodimentof the present invention;

FIG. 2 is a layout view of signal lines in a fan-out area of a TFT arraypanel according to a first embodiment of the present invention;

FIG. 3 is a layout view of signal lines in a fan-out area of a TFT arraypanel according to a second embodiment of the present invention.

FIG. 4 is a graph illustrating the RC delays of the signal lines on thefan-out areas of the TFT array panel according to the first and thesecond embodiments of the present invention compared with the RC delayof a conventional TFT array panel;

FIG. 5 is a layout view of signal lines in a fan-out area of a TFT arraypanel according to a third embodiment of the present invention;

FIG. 6 is a layout view of signal lines in a fan-out area of a TFT arraypanel according to a fourth embodiment of the present invention;

FIG. 7A is a graph illustrating the RC delay of the signal lines on thefan-out areas of a conventional TFT array panel;

FIG. 7B is a graph illustrating the RC delay of the signal lines on thefan-out areas of a TFT array panel according to the third embodiment ofthe present invention;

FIG. 7C is a graph illustrating the RC delay of the signal lines on thefan-out areas of a TFT array panel according to the fourth embodiment ofthe present invention;

FIG. 8 is a sectional view of signal lines on a gate fan-out area of aTFT array panel according to a fifth embodiment of the presentinvention;

FIG. 9 is a sectional view of signal lines on a gate fan-out area of aTFT array panel according to a sixth embodiment of the presentinvention;

FIG. 10 is a sectional view of signal lines on a data fan-out area of aTFT array panel according to a seventh embodiment of the presentinvention; and

FIG. 11 is a sectional view of signal lines on a data fan-out area of aTFT array panel according to an eighth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the present invention are shown. The present invention may, however,be embodied in many different forms and should not be construed aslimited to the embodiments set forth herein.

In the drawings, the thickness of layers and regions are exaggerated forclarity. Like numerals refer to like elements throughout. It will beunderstood that when an element such as a layer, region or substrate isreferred to as being “on” another element, it can be directly on theother element or intervening elements may also be present. In contrast,when an element is referred to as being “directly on” another element,there are no intervening elements present.

Now, panels for liquid crystal displays (LCDs) according to embodimentsof the present invention will be described in detail with reference tothe accompanying drawings for one of ordinary skill in the art to easilycarry out.

A TFT array panel according to an embodiment of the present inventionwill be described with reference to FIG. 1, which illustrates an LCDincluding a TFT array panel according to an embodiment of the presentinvention.

An LCD including a TFT array panel according to an embodiment of thepresent invention includes a TFT array panel 1 and a color filter arraypanel 2 opposite each other and a liquid crystal layer (not shown)interposed between the TFT array panel 1 and the color filter arraypanel 2.

Regarding the color filter array panel 2, there are provided a pluralityof red, green and blue color filters (not shown), a black matrix (notshown) defining a plurality of pixel areas, and a common electrode (notshown).

The TFT array panel 1 according to an embodiment of the presentinvention includes a plurality of gate lines 121 extending in atransverse direction and transmitting scanning signals, a plurality ofdata lines 171 intersecting the gate lines 121 to define a plurality ofpixel areas and transmitting image signals, a plurality of pixelelectrodes (not shown) located on the pixel areas arranged in a matrixand made of transparent conductive material such as indium tin oxide(“ITO”) and indium zinc oxide (“IZO”) or reflective conductive material,and a plurality of TFTs (not shown) located at the intersections of thegate lines 121 and the data lines 171 and connected to the gate lines121 and the data lines 171 to control the image signals to be applied tothe pixel electrodes in response to the scanning signals.

In the meantime, the TFT array panel 1 includes a display area D fordisplaying images, a plurality of pad areas and a plurality of fan-outareas GF and DF located between the display area and the pad areas. Thedisplay area D includes the pixel areas defined by the intersections ofthe signal lines 121 and 171. Each pad area is provided with a pluralityof gate pads (not shown) for transmitting the scanning signals from anexternal device to the gate lines 121 or a plurality of data pads (notshown) for transmitting the image signals from an external device to thedata lines 171. Each fan-out area is provided for connecting the signallines 121 and 171 to the clustered pads.

Although the color filters, the black matrix and the common electrode inthis embodiment are provided on the color filter array panel 2, they maybe provided on the TFT array panel 1.

The pad areas are connected to a plurality of gate driving integratedcircuits (“ICs”) 420 and a plurality of data driving ICs 430 mounted byout lead bonding (“OLB”). A plurality of conductors 93 are provided onthe fan-out areas GF and DF and overlap the gate lines 121 or the datalines 171. The conductors 93 are connected to a common electrode voltageto reduce the RC delay due to the difference in length between thesignal lines 121 and 171 on the fan-out area GF and DF. Alternatively,the conductors 93 are floated. The width of each conductor 93 variesdepending on the length of the signal lines 121 and 171, e.g., the widthincreases as the length of the signal line 121 and 171 overlapping theconductor 93 decreases.

Fan-out areas of TFT array panels according to embodiments of thepresent invention will be described more in detail below.

The embodiments illustrate an exemplary chip on glass (“COG”) type LCDwhere the gate driving ICs 420 and the data driving ICs 430 are mounteddirectly on the TFT array panel 1 using OLB. Alternatively, the drivingICs 420 and 430 may be mounted on a separate panel or films (e.g., tapecarrier package type (“TCP”)).

FIG. 2 is a layout view of signal lines in a fan-out area of a TFT arraypanel according to a first embodiment of the present invention.

The width of the signal lines 121 and 171 of a TFT array panel accordingto a first embodiment of the present invention are equal to each otherand the signal lines 121 and 171 overlap the conductor 93. The width ofeach conductor 93 is largest at the overlap with the shortest one amongthe signal lines 121 and 171 and decreases as the length of the signallines 121 and 171 overlapping the conductor 93 increases. When a groupof signal lines L1-Ln connected to one IC on the fan-out area aresymmetrically arranged, the conductor 93 is the widest at the center andbecomes narrow as it goes to ends.

The conductors 93 include the same layer made of a transparentconductive material such as ITO and IZO as the pixel electrodes.Alternatively, the conductors 93 are preferably made of Al alloy. Theconductors 93 may include the same layer as the signal lines 121 or 171.The conductors 93 overlapping the gate lines 121 preferably include thesame layer as the data lines 171, e.g., to be made of the same materialas the data lines 171, while the conductors 93 overlapping the datalines 171 preferably include the same layer as the gate lines 121, e.g.,to be made of the same material as the gate lines 121.

The conductors 93 are connected to the common voltage via dummy pins ofICs.

The capacitance between the conductors 93 and the signal linescompensates for the difference in resistance and capacitances betweenthe signal lines.

FIG. 3 is a layout view of signal lines 121, 171 in a fan-out area of aTFT array panel according to a second embodiment of the presentinvention.

A plurality of conductors 93 overlapping signal lines 121 and 171 areprovided on a TFT array panel 1 according to a second embodiment of thepresent invention. The width of each conductor 93 is largest at theoverlap with the shortest one among the signal lines 121 and 171 anddecreases as the length of the signal lines 121 and 171 overlapping theconductor 93 increases, like the first embodiment. In addition, a groupof signal lines L1-Ln connected to one IC on the fan-out area aresymmetrically arranged like the first embodiment.

Differently, the width of the signal lines 121 and 171 increases inproportion to their lengths. The increase of the width in proportionalto the length is intended to make the resistances of the signal lines121 and 171 equal. For example, high resistance of a signal lineincluding a long portion on the fan- out area is compensated by thisconfiguration. In the fan-out area having a symmetrical arrangement ofthe signal lines L1 and Ln connected to one IC according to thisembodiment, the width of the signal lines decreases as it goes to thecenter while the width increases as it goes to the ends.

The RC delay becomes much more uniform by providing the conductors 93for compensating the difference in the capacitances and by widening thesignal lines 121 and 171 in proportion to their lengths for compensatingthe difference in the resistances.

Only the variation of the width of the signal lines without theprovision of the conductor may compensate the RC delay. However, thewidthwise variation is limited by practical processes such as thelimitation of the distance between the signal lines due to theresolution of light exposers, the limitation of the width of the signallines due to the etching errors, and the marginal consideration of acutting process for cutting the substrates to separate them into aplurality of cells for LCDs. Accordingly, only the variation of thewidth of the signal lines without the conductor may not fully compensatethe difference in the RC delay between the signal lines.

FIG. 4 is a graph illustrating the RC delay of signal lines on a fan-outarea of a TFT array panel according to the first and the secondembodiments of the present invention compared with the RC delay of aconventional TFT array panel. The abscissa of FIG. 4 indicates thepositions of the signal lines connected to one IC. For example, L1 andLn indicate the leftmost and the rightmost signal lines, respectively.

The lowermost curve 10 shown in FIG. 4 represents the RC delay of thesignal lines of a conventional TFT array panel without any compensationfor RC delay. The intermediate curve 20 represents the RC delay of thesignal lines of a TFT array panel with conductors 93 according to thefirst embodiment. The uppermost curve 30, which is nearly a straightline, represents the RC delay of the signal lines with different widthsof a TFT array panel with conductors 93 according to the secondembodiment.

FIG. 4 suggests that the provision of the conductors 93 and thevariation of the line width of the signal lines make the RC delayuniform.

FIG. 5 is a layout view of signal lines 121, 171 in a fan-out area of aTFT array panel according to a third embodiment of the presentinvention.

According to the third embodiment, the arrangement of the signal lines121 and 171 connected to one IC 420, 430 on the fan-out area areasymmetrical. However, a rule that the width of the conductor 93decreases as the length of the signal lines 121 and 171 overlapping theconductor 93 increases is also applied to this embodiment like the firstembodiment. Under this rule, the conductor 93 has various shapesdepending on the arrangement of the signal lines 121 and 171 on thefan-out area.

FIG. 6 is a layout view of signal lines 121, 171 in a fan-out area of aTFT array panel according to a fourth embodiment of the presentinvention.

According to the fourth embodiment, the arrangement of the signal lines121 and 171 connected to one IC 420, 430 on the fan-out area areasymmetrical. However, a rule that the width of the conductor 93decreases as the length of the signal lines 121 and 171 overlapping theconductor 93 increases and the width of the signal lines 121 and 171increases in proportion to their length is also applied to thisembodiment like the second embodiment. Under this rule, the conductor 93has various shapes depending on the arrangement of the signal lines 121and 171 on the fan-out area.

FIG. 7A is a graph illustrating the RC delay of the signal lines on thefan-out areas of a conventional TFT array panel, FIG. 7B is a graphillustrating the RC delay of the signal lines on the fan-out areas of aTFT array panel according to the third embodiment of the presentinvention, and FIG. 7C is a graph illustrating the RC delay of thesignal lines on the fan-out areas of a TFT array panel according to thefourth embodiment of the present invention.

As shown in FIG. 7A, the extreme variation of the RC delay deterioratesthe image quality since the discontinuity in the RC delay appears as adiscontinuous line on a screen. As shown in FIGS. 7B and 7C, theprovision of the conductors 93 and the variation of the line width ofthe signal lines make the RC delay uniform, thereby preventing thedeterioration of the image quality.

Now, cross-sections of fan-out areas according to embodiments of thepresent invention will be described with reference to the drawings.

FIG. 8 is a sectional view of signal lines on a gate fan-out area of aTFT array panel according to a fifth embodiment of the presentinvention.

A plurality of gate lines 121 is formed on an insulating substrate 110,and a gate insulating layer 140 is formed on the gate lines 121. Aconductor 93 made of the same material as data lines (not shown) isformed on the gate insulating layer 140, and a passivation layer 180 isformed on the conductor 93. A plurality of pixel electrodes (not shown)are formed on the passivation layer 180.

FIG. 9 is a sectional view of signal lines on a gate fan-out area of aTFT array panel according to a sixth embodiment of the presentinvention.

Different from the fifth embodiment, a conductor 93 made of the samematerial as pixel electrodes (not shown) is formed on a passivationlayer 180.

FIG. 10 is a sectional view of signal lines on a data fan-out area of aTFT array panel according to a seventh embodiment of the presentinvention.

A conductor 93 made of the same material as gate lines (not shown) isformed on an insulating substrate 110, and a gate insulating layer 140is formed on the conductor 93 and the gate lines. A plurality of datalines 171 is formed on the gate insulating layer 140, and a passivationlayer 180 is formed on the data lines 171. A plurality of pixelelectrodes (not shown) are formed on the passivation layer 180.

FIG. 11 is a sectional view of signal lines on a data fan-out area of aTFT array panel according to an eighth embodiment of the presentinvention.

Different from the seventh embodiment, a conductor 93 made of the samematerial as pixel electrodes (not shown) is formed on a passivationlayer 180.

According to the present invention, the difference in the RC delays dueto the different lengths of signal lines on a fan-out area of a TFTarray panel is compensated for by providing a conductor anddifferentiating the width of the signal lines.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be made thereto withoutdeparting from the spirit and scope of the present invention as setforth in the appended claims.

1. A thin film transistor array panel comprising: an insulatingsubstrate; a plurality of gate lines formed on the insulating substrate,each gate line including a pad for connection to an external device; aplurality of data lines intersecting the gate lines and insulated fromthe gate lines, each data line including a pad for connection to anexternal device; and a plurality of conductors respectively overlappingat least one of the gate lines and the data lines, wherein capacitancebetween the gate lines or the data lines and the conductors decreases asa length of the gate lines or the data lines increases.
 2. The thin filmtransistor array panel of claim 1, wherein each data line comprises apad portion including the pad, a display portion and a fan-out portionconnecting the display portion and the pad portion, and resistance perunit length of the fan-out portion of the data line decrease as a lengthof the fan-out portion of the data line increases.
 3. The thin filmtransistor array panel of claim 1, wherein each gate line comprises apad portion including the pad, a display portion and a fan-out portionconnecting the display portion and the pad portion, and resistance perunit length of the fan-out portion of the gate line decrease as a lengthof the fan-out portion of the gate line increases.
 4. The thin filmtransistor array panel of claim 1, wherein the conductors are appliedwith a reference voltage.
 5. The thin film transistor array panel ofclaim 1, further comprising a pixel electrode located on a pixel areadefined by intersections of the gate lines and the data lines, whereinthe conductors are formed substantially in a same layer and of a samematerial as the pixel electrode.
 6. The thin film transistor array panelof claim 1, wherein the conductors overlap the gate lines, wherein theconductors are formed substantially in a same layer and of a samematerial as the data lines.
 7. The thin film transistor array panel ofclaim 1, wherein the conductors overlap the data lines, wherein theconductors are formed substantially in a same layer and of a samematerial as the gate lines.
 8. The thin film transistor array panel ofclaim 1, wherein the conductors include first conductive segmentsoverlapping the gate lines and second conductive segments overlappingthe data lines, the first conductive segments are formed substantiallyin a same layer and of a same material as the data lines, and the secondconductive segments are formed substantially in a same layer and of asame material as the gate lines.
 9. The thin film transistor array panelof claim 1, wherein the conductors are floated.
 10. A thin filmtransistor array panel comprising: an insulating substrate; a pluralityof gate lines formed on the insulating substrate, each gate lineincluding a pad for connection to an external device; a plurality ofdata lines intersecting the gate lines and insulated from the gatelines, each data line including a pad for connection to an externaldevice; and a plurality of conductors respectively overlapping at leastone of the gate lines and the data lines, wherein overlapping areabetween the gate lines or the data lines and the conductors decreases asa length of the gate lines or the data lines increases.
 11. The thinfilm transistor array panel of claim 10, wherein each data linecomprises a pad portion including the pad, a display portion and afan-out portion connecting the display portion and the pad portion, andresistance per unit length of the fan-out portion of the data linedecrease as a length of the fan-out portion of the data line increases.12. The thin film transistor array panel of claim 10, wherein each gateline comprises a pad portion including the pad, a display portion and afan-out portion connecting the display portion and the pad portion, andresistance per unit length of the fan-out portion of the gate linedecrease as a length of the fan-out portion of the gate line increases.13. The thin film transistor array panel of claim 10, wherein theconductors are applied with a reference voltage.
 14. The thin filmtransistor array panel of claim 10, further comprising a pixel electrodelocated on a pixel area defined by intersections of the gate lines andthe data lines, wherein the conductors are formed substantially in asame layer and of a same material as the pixel electrode.
 15. The thinfilm transistor array panel of claim 10, wherein the conductors overlapthe gate lines, wherein the conductors are formed substantially in asame layer and of a same material as the data lines.
 16. The thin filmtransistor array panel of claim 10, wherein the conductors overlap thedata lines, wherein the conductors are formed substantially in a samelayer and of a same material as the gate lines.
 17. The thin filmtransistor array panel of claim 10, wherein the conductors include firstconductive segments overlapping the gate lines and second conductivesegments overlapping the data lines, the first conductive segments areformed substantially in a same layer and of a same material as the datalines, and the second conductive segments are formed substantially in asame layer and of a same material as the gate lines.
 18. The thin filmtransistor array panel of claim 10, wherein the conductors are floated.